1. Field of the Invention
The invention pertains to "T" drive bevel gear transmissions for louver type signs wherein a plurality of multifaced elongated louvers have indicia or images appearing on the faces thereof wherein pre-determined faces aligned in co-planar relationship produce a complete image, and partial simultaneous rotation of the louvers changes the appearance of the sign by making another louver indicia bearing face visible.
2. Description of the Related Art
Louver type signs require that a plurality of relatively long and narrow elements or louvers be mounted in side-by-side relationship wherein, as the louvers are indexed to present different faces for observation the longitudinal edges of adjacent louvers will be closely spaced as to permit a continuity of images appearing on a plurality of adjacent louver faces. The louvers are usually provided with three sides or faces, and the louvers are usually indexed at a pre-determined time cycle, such as to "show" a different louver face about every minute. Accordingly, with a three sided louver, the rate of indexing, or rotation, of a louver may be one-third of a revolution per minute.
In the past, it has been the common practice to simultaneously rotate or index the louvers constituting a complete sign by means of a belt or chain arrangement. Each of the louvers includes a drive mechanism operatively connected to a belt or chain system whereby a motor driving the belt or chain system will periodically operate to index the louvers to present a new visible louver face. With a three sided louver, only a 120.degree. rotation of the louver is required during each indexing cycle.
In order to provide optimum sign appearance wherein the images of adjacent louvers visibly blend and align with each other, it is necessary that the louvers accurately operate together and index accurately. Louver drive systems using belts and chains encounter a number of problems which adversely affects the operation and accuracy of indexing of the louvers. Malfunctioning will occur due to stretching or slipping of the belts or chains, breakage of the belts or chains, and problems occur maintaining the belts or chains in proper alignment in tracking and driving relationship to the associated sprocket or pulley.
With present transmissions for louver type signs, the dependability and long term maintenance-free operation desired has not been available, and louver type signs are expensive to operate and service.